Folliculogenesis: Development Of Follicles In Ovary


Folliculogenesis is the maturation of the ovarian follicles, is
a densely packed shell of somatic cells that contains an
immature oocytes. The ovary consists of an inner medulla and outer cortex with
indistinct boundaries, where medulla contains blood vessel and nerves while the
cortex is occupied by developing follicles.

Stages of Folliculogenesis:

Follicular development consists of follicles in different stages of development. They are
Primordial follicles
Primary follicles
Secondary follicles
Tertiary or Antral follicles
Pre-ovulatory follicles

What are primordial follicles?

The cortex of female ovary contains many number of
follicles. Primordial follicles contains immature egg
surrounded by flat, squamous granulose cells.

Primordial follicle stage:

At the time of birth primary oocytes are surrounded by thin,
single layer of epithelial cells where these are delimited from
the rest of ovarian stroma by thin basal lamina .
The primordial follicle always form the majority of the
follicle in ovary.

Primordial follicle development:

These primordial follicle contains immature oocytes
surrounded by flat, squamous granulosa cells(support cells)
that are segregated from the oocyte’s sourrounding by the
basal lamina.
Primordial follicle can be dormant for up to 50 years in the
human, the length of the ovarian cycle does not include this

Primordial follicles contain

A Primordial follicle
B Primary follicle
1 Oocyte
2 Follicular epithelium

How does the secondary follicle develop?

Stroma like cells are recruited by oocytes .The outer most layer surrounding follicle is basal lamina and became as theca externa and theca interna. An intricate connection of capillary vessels forms between the two layer of theca which begins to circulate blood to
follicles. The late term secondary follicle is histologically and structurally by gown oocyte surrounded by a zona pellucida its near nine layer of granulose cells. The develop of the antrum is start taking place in the secondary follicle stage .

Structure of Secondary follicles

1 Oocyte
2 Pellucid zone
3 Stratum granulosum
4 Theca folliculi cells

Antrum formation

The antral follicle is also called as Graafian follicle which is
the formation of fluid filled cavity adjacent to ooctye called
antrum and the follicle called antral follicle where contrast
called preantral follicle that are absent in antrum .

Early tertiary follicle

The basic structure of mature follicle has formation of no
novel cell are detectable. Granulose and theca cells continue to increase the antrum
volume. Tertiary follicle contains tremendous size and availability of
FSH which is not dependent on under the action of oocyte
secreted morphogenic gradient where the granulosa cells of
the tertiary follicle.

Early tertiary stage follicles

Tertiary follicle contains corona radiate which surrounded by zona pellucida
membrana which is interior basal lamina, periantral which is adjacent to antrum
cumulus oophorous which connect membrana and corona granulose
Theca interna cells express receptors for LH which includes
the production of androgen by the theca cells, here the
estrogen level will increase


Ovulation is the release of an egg from one of a woman’s
ovaries. After the egg is released, it travels down the fallopian tube,
where fertilization by a sperm cell may occur. Ovulation typically lasts one day and occurs in the middle of a woman’s menstrual cycle, about two weeks before she
expects to get her period.

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